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Flexural psoriasis

Psoriasis is a common scaly skin condition resulting in red scaly and thickened patches of skin. Flexural psoriasis is sometimes called inverse psoriasis and describes psoriasis localised to the skin folds and genitals. Common sites of flexural psoriasis are:

Armpits

Groin

Under the breasts

Umbilicus (navel)

Penis

Vulva

Natal cleft (between the buttocks)

Around the anus

Many patients have psoriasis affecting other sites, particularly inside the ear canal, behind the ears, through the scalp, and on elbows and knees.

Flexural psoriasis

Clinical features of flexural psoriasis

Due to the moist nature of the skin folds the appearance of the psoriasis is slightly different. It tends not to have silvery scale, but is shiny and smooth. There may be a crack (fissure) in the depth of the skin crease. The deep red colour and well-defined borders characteristic of psoriasis may still be obvious.

Scalyplaques may sometimes occur however, particularly on the circumcised penis.

Flexural psoriasis can be difficult to tell apart from seborrhoeicdermatitis, or may co-exist. Seborrhoeicdermatitis in skin folds tends to present as thin salmon-pink patches that are less well defined than psoriasis. If there is any doubt which is responsible, or there is thought to be overlap of the two conditions, the term sebopsoriasis may be used.

Complications of flexural psoriasis include:

Chaffing and irritation from heat and sweat

Secondary fungal infections particularly Candida albicans (thrush)

Lichenification (a type of eczema) from rubbing and scratching – this is a particular problem around the anus where faecal material irritates causing increased itching

Sexual difficulties because of embarrassment and discomfort

Thinned skin due to long term overuse of strong topical steroid creams

What is the treatment for flexural psoriasis?

Flexural psoriasis responds quite well to topical treatment but often recurs.

Topical steroids Weak topical steroids (often in combination with an antifungal agent to combat thrush) may clear flexural psoriasis but it will usually recur sometime after discontinuing treatment. Stronger topical steroids need to be used with care and only for a few days, thinly and very accurately applied to the psoriasis. If the psoriasis has cleared, stop the steroid cream. The steroid cream may be used again short-term when the condition recurs.

Overuse of topical steroids in the thin-skinned body folds may cause stretch marks, marked thinning of the skin and can result in long term aggravation of psoriasis (tachyphylaxis).

Vitamin D-like compoundsCalcipotriol cream is an effective and safe treatment for psoriasis in the flexures and should be applied twice daily. If it irritates, it can be applied once daily and hydrocortisone cream 12 hours later.

Strong topical agents Treatments that are tolerated in other sites are often too irritating to use in skin folds, e.g., dithranol, salicylic acid and coal tar. However, it may be possible to use them by diluting in emollients, or by applying them for short periods and washing off.

Systemic agents are rarely required for limited flexural psoriasis and phototherapy is relatively ineffective because the folds are hidden from light exposure.